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Preliminary Results of Laser Ranging to Un-cooperative Targets at Shanghai SLR Station
Yang FuMin, Zhang ZhongPing, Chen JuPing, Chen WanZhen, Wu ZhiBo, Zhang HaiFeng
Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China
Ivan Prochazka
Czech Technical University in Prague, Czech Republic
Email: [email protected]
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Goals
Investigation of the key techniques of
un-cooperative target laser ranging
Experimental laser ranging to
un-cooperative targets
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The returned signal strength of laser ranging on un-
cooperative targets can be estimated by:
20 2 4
cosq t rt r
t
E A Sn T K K
hc R
Estimate of the returned signal strength
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Where
n0: Average number of photoelectrons received by detector
λ: Wavelength of laser, 532nm
ηq: Quantum efficiency of the C-SPAD detector, 0.2
h: Planck constant, 6.624×10-34 J·S
c: Light speed, 2.998×108 m/s
Et: Energy of laser pulse, 2J
Ar: Effective area of receive telescope, 0.245m2
ρ: Reflectivity of the target’s surface
r: Equivalent radius of the target, 1m
cos(): Suppose the targets are spherical, cos()=1
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We have,We have,
n0=0.198 (Photoelectron)
t: Divergency of laser beam from telescope, 12 arcsec
R: Range of the targets, 800Km
T: Atmospheric transmission, T2=0.6
Kt: Eff. of transmitting optics, 0.60
Kr: Eff. of receiving optics, 0.60
: Attenuation factor, 13dB
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The probability of detection can be estimated:
So we can get 18 return signals in 5 second by the
laser with 20Hz repetition.
0 0.1981 1 0.18nP e e
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1: HR mirror 2: E-Q Switch 3: Polarizer 4: YAG rod 5: Output mirror 6: Isolator 7: Compensator
8: Reflect mirror 9: Frequency doubler 10: Optical coupler 11: Imaging lens
Beams combinationAmplifier Unit 2
Amplifier Unit 1 Isolator
Isolator Oscillator
Diagram of the 40W laser (2J, 20Hz, 10ns)
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Photo of the laser
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Inner view of the laser
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Laser firing at Shanghai
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Some results of
un-cooperative target laser ranging
at the Shanghai SLR station
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Returns from the discard Soviet rocket (ID 1987-38B) on July 7, 2008
Number of point: 127RMS: 76cm
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Returns from the discard US rocket (ID 2007-006G) on July 17, 2008
Number of point: 79RMS: 83cm
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Returns from the discard US rocket (ID 2007-006G) on July 18, 2008
Number of point: 170RMS: 68cm
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Ranging data of ID 1987-38B on July 7, 2008
2008 07 07年 月 日
700750
800850
900950
1000
46230 46250 46270 46290 46310 46330
( )时间 秒
()
距离
值公
里
Time (s)
Ran
ge
(Km
)
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Ranging data of ID 2007-006G on July 17, 2008
2008 07 17年 月 日
700730760790820850880
71290 71300 71310 71320 71330 71340
( )时间 秒
()
距离
值公
里
Time (s)
Ran
ge
(Km
)
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Ranging data of ID 2007-006G on July 18, 2008
2008 07 18年 月 日
650
700
750
800
850
900
70200 70220 70240 70260 70280( )时间 秒
()
距离
值公
里
Time (s)
Ran
ge
(Km
)
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Statistics of returns (5-second bin) on July 7, 2008
12-14 returns in 5 seconds were obtained when tracking well, and roughly coincide with the estimation of the returns signal strength.
0
2
4
6
8
10
12
14
16
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17/5s时间
数据
点个
数
Time (5-second bin)
Nu
mb
er o
f re
turn
s
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Future Plan
• Upgrading of the prediction of the targets (now the error of range prediction is about 1km, too difficult to obtain the returns)
• Automatically scanning of range gate and rapidly identify the return signals
• To track smaller targets and assessing the ranging capability of the system
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The laser returns from the un-cooperative targets have
been obtained at the Shanghai SLR Station in July
2008.
These targets are the discard Soviet and US rockets
with the ID 1987-38B and 2007-006G respectively.
The return signals from the targets with the range of
900km were quite strong.
Summary
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Thank You!